Síntese e caracterização de compósito bactericida à base de caulinita-Ag para tratamento de água
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Data
2020-03-20
Autores
Guizellini, Filipe Corrêa
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Água é essencial para a vida e diversas tecnologias têm sido desenvolvidas para garantir a potabilidade desse recurso natural precioso, como os filtros a base de elementos naturais como argilas e fibras. Portanto, o objetivo desse trabalho foi sintetizar e caracterizar um novo compósito mineral estruturado a base de caulinita modificado com íons Ag+ e avaliar sua capacidade bactericida. A caracterização foi realizada por TG/DTA, FTIR com acessório de ATR, XRD e refinamento Rietveld, WD/XRF, FEG-SEM e por EDS; e avaliar a capacidade bactericida do novo compósito pelo teste de difusão do disco contra cepas de E. coli. Bco foi preparado em suspensão aquosa 1:100 (m/v) por 24 horas e seco a 60 oC por 12 horas (Bco_seco) e sinterizado a 1000 oC por 2 horas (Bco_sint), Pca4 foi também preparado sob suspensão, após inserida a Ag+ foi mantido em suspensão por mais 24 horas, após isso, a suspensão foi exposta à radiação UV em caixa fotocalítica, seca a 60 oC por 12 horas (Pca4_seco) e sinterizada a 1000 oC por 2 horas (Pca4_sint). As curvas TG/DTA do Bco_seco sugeriram a presença de caulinita (K), muscovita (M) e hidrotalcita (HT) pelos diferentes eventos de desidroxilação em diferentes atmosferas (ar sintético e N2). A interação argila Ag ocorreu com a fase hidrotalcita, como pode ser verificado pelo desaparecimento do evento a 430 oC (N2) e 446 oC (ar). Os resultados de FTIR permitiram evidenciar que a modificação ocorreu devido às alterações observadas na faixa de (750 ≤ ν ≤ 1350) cm-1 para as ligações -OH internos e Si-O. A composição da amostra Bco_seco qualificada por XRD e quantificada por Refinamento Rietveld, e as fases cristalinas presentes são quartzo (Q), calcita (C), K, HT, M e portlandita (P). Após a sinterização, o compósito apresentou a formação de novas fases cristalinas, devido à desidroxilação dos argilominerais presentes na mistura. Quando modificada com espécies de Ag, a amostra não apresentou picos característicos de HT, permitindo sugerir, a interação entre HT e espécies de Ag. As composições elementares, estimadas para todas as amostras por WD/XRF foram Si, Al, Ca, K, Mg, Fe, Ti e Ag. Após a modificação com as espécies de Ag, a quantidade relativa da Ag aumentou para os compósitos Pca4_seco e Pca4_sint. As imagens SEM mostraram a estrutura hexagonal característica de argilas sobrepostas em camadas e possibilitou elucidar a formação de uma nova fase não cristalina após a interação com as espécies de Ag. O novo material apresentou capacidade bactericida e pode atender ao controle de qualidade microbiológico de potabilidade da água.
Water is essential for life and several technologies have been developed to guarantee the potability of this precious natural resource, such as filters based on natural elements such as clays and fibers. Therefore, the aim of this work was to synthesize and characterize a new structured silver-clay dried, calcined or sintered at different temperatures composite by TG/DTA analysis, FTIR spectrometry analysis, XRD and Rietveld Refinement, WD/XRF spectrometry, FEG-SEM images, and EDS chemical analysis; and to evaluate the antibacterial capacity of the new composite by the diffusion disk test against E. coli strains to attend water potability parameters. Bco was prepared in aqueous suspension 1: 100 (m/v) for 24 hours and dried at 60 oC for 12 hours (sample Bco_dried) and sintered at 1000 oC for 2 hours (sample Bco_sint), Pca4 was also prepared under suspension, after being inserted at Ag+ was kept in suspension for another 24 hours, after that, the suspension was exposed to UV radiation in a photocalytic box, dried at 60 oC for 12 hours (sample Pca4_dried) and sintered at 1000 oC for 2 hours (sample Pca4_sint). TG/DTA curves of Bco_dried suggested the presence of kaolinite, muscovite and hydrotalcite by the different events of structural water loss at different atmospheres. The interaction of Ag-clay might have occurred with hydrotalcite as can be inferred by the disappearance of the event at 430 oC (N2) and 446 oC (air). FTIR spectra showed that the modification occurred because of the changes that can be observed in the band range of (750 ≤ ν ≤ 1350) cm-1 for inner -OH and Si-O bonds. The Bco_dried composition was quantified by XRD and Rietveld Refinement, and crystalline phases are quartz, calcite, kaolinite, hydrotalcite, muscovite and portlandite. After sintering, the material presented the formation of new crystalline phases, due to the loss of structural water. When modified, the sample had no characteristic peaks of hydrotalcite, suggesting an interaction with Ag species. The compositions estimated for all samples by WD/XRF are mostly of Si, Al, Ca, K, Mg, Fe, Ti, and Ag. After modification, Ag increased significantly for Pca4_dried and Pca4_sint. SEM images presented the hexagonal characteristic of layered clay material and showed the interaction with Ag added. From the results, under the mentioned conditions, the new material can be applied effectively in the manufacture of water purification candles with the capacity to inhibit bacterial growth to meet the microbiological parameters of water potability.
Water is essential for life and several technologies have been developed to guarantee the potability of this precious natural resource, such as filters based on natural elements such as clays and fibers. Therefore, the aim of this work was to synthesize and characterize a new structured silver-clay dried, calcined or sintered at different temperatures composite by TG/DTA analysis, FTIR spectrometry analysis, XRD and Rietveld Refinement, WD/XRF spectrometry, FEG-SEM images, and EDS chemical analysis; and to evaluate the antibacterial capacity of the new composite by the diffusion disk test against E. coli strains to attend water potability parameters. Bco was prepared in aqueous suspension 1: 100 (m/v) for 24 hours and dried at 60 oC for 12 hours (sample Bco_dried) and sintered at 1000 oC for 2 hours (sample Bco_sint), Pca4 was also prepared under suspension, after being inserted at Ag+ was kept in suspension for another 24 hours, after that, the suspension was exposed to UV radiation in a photocalytic box, dried at 60 oC for 12 hours (sample Pca4_dried) and sintered at 1000 oC for 2 hours (sample Pca4_sint). TG/DTA curves of Bco_dried suggested the presence of kaolinite, muscovite and hydrotalcite by the different events of structural water loss at different atmospheres. The interaction of Ag-clay might have occurred with hydrotalcite as can be inferred by the disappearance of the event at 430 oC (N2) and 446 oC (air). FTIR spectra showed that the modification occurred because of the changes that can be observed in the band range of (750 ≤ ν ≤ 1350) cm-1 for inner -OH and Si-O bonds. The Bco_dried composition was quantified by XRD and Rietveld Refinement, and crystalline phases are quartz, calcite, kaolinite, hydrotalcite, muscovite and portlandite. After sintering, the material presented the formation of new crystalline phases, due to the loss of structural water. When modified, the sample had no characteristic peaks of hydrotalcite, suggesting an interaction with Ag species. The compositions estimated for all samples by WD/XRF are mostly of Si, Al, Ca, K, Mg, Fe, Ti, and Ag. After modification, Ag increased significantly for Pca4_dried and Pca4_sint. SEM images presented the hexagonal characteristic of layered clay material and showed the interaction with Ag added. From the results, under the mentioned conditions, the new material can be applied effectively in the manufacture of water purification candles with the capacity to inhibit bacterial growth to meet the microbiological parameters of water potability.
Descrição
Palavras-chave
Minerais de argila, Atividade bactericida, Filtro de argila, Difratometria de Raios X, Refinamento Rietveld, TG/DTA, Clay minerals, Antibacterial activity, Clay filter, X-ray diffractometry, Rietveld refinement, TG/DTA